1. Field of the Invention
The present invention relates to a virtual LAN system and, particularly, to a virtual LAN system in which a virtual LAN is constructed every protocol.
2. Description of Related Art
In order to construct a plurality of virtual LAN's every protocol indicative of communication procedures in a virtual LAN system of this kind, it has been usual, as disclosed in Japanese Patent Application Laid-open No. Sho 64-54954, to determine a protocol higher in level than a network layer of OSI reference model used in a communication every LAN (referred to as "upper protocol", hereinafter) such that a communication is possible in a LAN according to only the determined protocol.
The term "virtual LAN" in this description means a LAN which services a host terminal by connecting the host terminal to the LAN through not a physical port of the host terminal but a logical connection.
Further, in order to enable the host terminal to belong to a plurality of virtual LAN's, virtual LAN's to which the host terminal can belong are preliminarily registered in a virtual server for controlling the construction of the virtual LAN's and a connection is made to the virtual LAN server by assigning the virtual LAN to be used in a communication when the host terminal starts the communication.
Since such conventional virtual LAN system determines the upper protocol to be used in a communication every LAN in order to construct a plurality of virtual LAN's every protocol indicative of the communication procedures, a communication within the LAN must be performed by using only this protocol. Therefore, there is a problem that the host terminal can not perform communication by using a plurality of upper protocols within the connected LAN. Further, since, in order to enable the host terminal to belong to a plurality of virtual LAN's, virtual LAN's to which the host terminal can belong are preliminarily registered in a virtual server for controlling the construction of the virtual LAN's and a connection is made to the virtual LAN server by assigning the virtual LAN to be used in a communication when the host terminal starts the communication, there is another problem that can not use other virtual LAN's than the virtual LAN to which the connection is made.